The present disclosure relates to field effect transistors (“FETs”) with high mobility quantum well channels and engineered density of states (“DOS”), and more specifically, to complementary field effect transistors with abrupt switching of channel carrier density and drain current.
Prior art high mobility metal-oxide-semiconductor field effect transistors (“MOSFETs”) form the conducting channel in high mobility bulk materials (see, e.g., Y. Xuan et al., “High Performance submicron inversion-type enhancement-mode InGaAs MOSFETs with ALD Al2O3, HfO2 and HfAlO as gate dielectrics,” IEDM Tech Dig., p. 637 (2007)) or high-mobility quantum wells cladded by a higher band gap semiconductor layer (see, e.g., R. J. W. Hill et al., “1 μm gate length, In0.53Ga0.47As channel thin body n-MOSFET on InP substrate with transconductance of 737 μS/μm,” Electron Lett., Vol. 44, p. 498 (2008)). The effective electron mass of bulk materials with high mobility such as In0.53Ga0.47As is small (mn=0.044) resulting in low effective density of states (DOS∝mn) which can limit maximum device current. Typical cladding layers such as In0.5Al0.5As have only somewhat higher mass (mn=0.086) and fail to substantially raise the unified electron effective mass mn in a quantum well design.
Prior art MOSFETs rely on thermal activation of charge carriers and are limited to a subthreshold swing S of 60 mV/dec at room temperature. For scaled CMOS devices, S easily exceeds 100 mV/dec due to short channel effects. This causes substantial source-drain leakage and excessive power dissipation as well as heat generation and limits the performance of scaled CMOS circuits.